What is Reverse DNS (rDNS)?
Reverse DNS is, quite simply, the inverse process of normal DNS - or 'forward' DNS. You can find out more about forward DNS here.
In short, rDNS allows an IP address to be resolved back to a domain name, the direct opposite of standard DNS. This process authenticates a domain name with the IP address the data has been sent from, avoiding common spamming techniques including sending emails/data from domain names that are not properly authenticated. If, for example, somebody tried to send an email to a client from a businesses domain (lets say mail.netwisehosting.co.uk) without rDNS, the clients mailbox may reject the email as it would be unable to use a Reverse DNS record to verify the IP against the domain of the sender.
Essentially, rDNS is a method of verifying sender IP address information against authenticated domain names, much like return to sender addresses on post giving an authentic route back to the original sender. Many mailboxes require rDNS entries to accept inbound mail as part of their spam filtering, as unresolved/unauthenticated IP's/domains are not trusted by many email policies.
If you would like to know more about rDNS, or how you can setup and manage rDNS in your My Netwise Hosting Control Panel, please do not hesitate to contact your account manager.